Nowadays, irrigated agriculture accounts for about 70 percent of water withdrawn worldwide from lakes, rivers and aquifers, thus being the greatest human intervention in the water cycle. In the last 40 years, global agricultural production has more than doubled (although cropland has increased by only 12 percent) in part through increased reliance on irrigation. Even though irrigated lands account for only 17 percent of total croplands, they produce 40 percent of food worldwide, and it is foreseen to increase in the next decades. As the earth's population increase in the future, the demand for food will increase. To supply this growing demand, the entire world, and especially arid and semi-arid regions, will require a significant expansion and intensification of the irrigation agriculture.

Particularly in the Mediterranean Basin, which is a focus area for this proposal, irrigated areas have doubled in the last 40 years but their sustainability currently face critical problems due to urbanization pressure, market volatility and climate variability with increased recurrence and intensity of drought periods. This evidence has caused a shift towards demand management of irrigation with a strong interest in reducing water withdrawals and increasing irrigation efficiency.

In this context the knowledge of the distribution and the extent of irrigated areas as well as the amount of water used by irrigation is central for: 1) modelling irrigation water requirements at the global scale, 2) assessing irrigated food production, and 3) quantifying the impact of irrigation on climate, river discharge and groundwater depletion. Notwithstanding its recognized importance, obtaining high-quality information about the actual irrigated areas worldwide is nontrivial and the problem is much more pronounced in terms of quantification of the water actually used for irrigation. This problem is evidenced in most of large scale hydrological/land surface models that do not include irrigation among the modelled processes.